Editing Cytogenetics (section)

===Fluorescence in situ hybridization===
[[Image:Bcrablinter.jpg|right|thumb|Interphase cells positive for a t(9;22) rearrangement]]
[[Fluorescence in situ hybridization]] (FISH) refers to using fluorescently labeled probe to hybridize to cytogenetic cell preparations.

In addition to standard preparations FISH can also be performed on:
* [[Bone marrow examination|bone marrow smears]]
* [[Blood film|blood smears]]
* paraffin embedded tissue preparations
* enzymatically dissociated tissue samples
* uncultured bone marrow
* uncultured [[amniocyte]]s
* [[Cytospin]] preparations

====Slide preparation====
''This section refers to the preparation of standard cytogenetic preparations''

The slide is aged using a salt solution usually consisting of 2X SSC (salt, sodium citrate). The slides are then dehydrated in [[ethanol]], and the probe mixture is added. The sample [[DNA]] and the probe DNA are then co-denatured using a heated plate and allowed to re-anneal for at least 4 hours. The slides are then washed to remove the excess unbound probe, and counterstained with 4',6-Diamidino-2-phenylindole ([[DAPI]]) or propidium iodide.

====Analysis====
Analysis of FISH specimens is done by [[fluorescence microscope|fluorescence microscopy]] by a clinical laboratory specialist in cytogenetics. For oncology, generally, a large number of [[interphase]] cells are scored in order to rule out low-level residual disease, generally between 200 and 1,000 cells are counted and scored. For congenital problems usually 20&nbsp;metaphase cells are scored.{{cn|date=February 2024}}